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2 What Is ISA? Instruction set architecture is the structure of a computer that a machine language programmer (or a compiler) must understand to write a correct (timing independent) program for that machine. For IBM System/360, 1964  Class ISA types: Stack, Accumulator, and General-purpose register  ISA is mature and stable –Why do we study it?

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11 Memory Addressing Instructions see registers, constant values, and memory  Addressing mode decides how to specify an object to access –Object can be memory location, register, or a constant –Memory addressing is complicated  Memory addressing involves many factors –Memory addressing mode –Object size –byte ordering –alignment For a memory location, its effective address is calculated in a certain form of register content, immediate address, and PC, as specified by the addressing mode